ND Filter & GoPro = Cinematic FPV Videos without Jello?!

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Does ND filter on GoPro cameras actually remove jello and make your FPV videos look more cinematic? We are going to find out in this post, and I will also explain what an ND filter is, and how ND filter affect GoPro image quality.

What is ND Filter?

ND stands for “Neutral Density”. Ideally, an ND filter can equally (or neutrally) reduce the amount of light across the entire spectrum entering your camera sensor without changing the image color. In a nutshell, it’s a pair of sun glasses for you camera! :)

Here is an example of before and after applying an ND16 filter on my GoPro Session.

From my understanding, ND filters are often use in high light situations, where you are unable to lower shutter speed. This creates realistic motion blur and reduces jello (vibration in your video). However it’s not as useful in dark environment as it lowers brightness.

In this video I tested ND4 and ND16 filters under the same lighting condition and see how they affect the image quality.

ND Filter Removes Jello?

As you can see from my testing, ND filters can indeed reduce the amount of jello in the FPV footage. The higher degree the filter, the more effective it is.

The GoPro uses rolling shutter, when there is vibration in the quadcopter, it results in jello in the footage. The shutter speed on GoPro cameras is automatic by default, brighter sunlight will increase the shutter speed. Adding an ND filter slows reduces the amount of light that enters the camera, which leads to slower shutter speed and thus less artifacts and jello.

Jello can be caused by badly tuned PID, or maybe the motors have bad bearings. Even if you had done everything properly, one bent propeller is enough to cause your drone to oscillate and ruin your FPV video!

It’s impossible to make sure your quad is perfect in every flight, that’s what makes ND filters so powerful for minimizing jello on your GoPro camera.

ND Filter Makes FPV Videos More Cinematic?

There are a lot of talks about how ND filters can make FPV videos look more cinematic. I guess it depends on what the definition of “cinematic” is. My observation is that ND filter introduces more motion blur to the footage, and that video effect is very special and unique.

Similar effect can be achieved when filming at sunset. Because of the low light, the camera has to lower the shutter speed in order to capture enough light for the footage to not look too dark. And the lowered shutter speed can cause motion blur. Perhaps this is what helps to reduce jello too.

By using ND filters, we can recreate similar effect even on a bright sunny day, without getting our footage over-exposed.

What ND Filter to Get for the GoPro Session?

The number indicates the amount of light reduction, larger number means more reduction. You can stack an ND filter on top of another to increase the reduction, for examples:

ND2 + ND4 = ND8

ND4 + ND4 = ND16

ND4 + ND8 = ND32

I prefer to use an ND8 or ND16 for sunny days, and an ND2 or ND4 for cloudy days. But of course this is a personal preference and depends heavily on the environment and lighting condition.

When I was searching for ND filters for my GoPro Hero5 Session, there weren’t many options because I am using a TPU mount. Those “add-on module” type simply won’t work. The closest solution was the simple “sticky film” type which you can apply directly on the glass. You can find them at GetFPV:

They are very handy because they stick right on the GoPro without glue or any help. If it gets dirty, you can just wash it with water and it will stick again.

But when it comes to image quality, they aren’t that great I am afraid. First of all, there are bubbles that I couldn’t completely remove, and you can see the tiny bits of refection in the video. And it can get permanent wrinkles if you roll or fold it. Lastly due to the surface curvature, the brightness can be uneven, the edges seem to be darker than the center.

I think the they are good enough if you just want to experiment.

Update (Aug 2018): Some have suggested that these are just 35% window tint.

Session ND Filters Pack from Amazon

Next I am trying this ND filter pack from Amazon. It comes with a cap that sits directly on top of the session, and it allows you to slide the filter in. The pack comes with 4 filter options: ND2, ND4, ND8 and ND16: https://amzn.to/2HdZJbr

Result:

The solution works well, but there are some strange sun flare. Some people might prefer it, some might hate it. I think it’s kind of special effect and anyway this is still better than using the “stick-on” type of filter IMO.

The quality is okay, but it’s plastic not glass, so you might get scratches more easily.

To install it, I just tie a rubber band to the holes in the handles of the cap using zip ties. The rubber band will hold the cap tightly to the session.

Other Options

Another popular option is the TBS Jello Guard (GetFPV). It’s designed for the Hero3 and Hero4, but with a 3D printed case you can also use it for the Session.

I realize how much easier it is with the standard size GoPro, such as the Hero5 and Hero6. You can get push on ND filter lenses.